# AJL - condensed matter



## [Reflections on the past, present and future of condensed matter physics](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/4716/reflections%2Bleggett.pdf)

- (mini?) Paradigm shifts in CMP

Landa-Fermi liquid - 1956
BCS - 1957
RG and 2nd order transitions - 1963-71
FQHE
quantum information - [it from bit](https://knowen.org/nodes/27847?path=1-24392-26506-27833-27847)

- mentioned briefly

>  one thinks of superfluid 3-He (1972), the integral quantum Hall effect (1980), cuprate superconductivity (1986), and most recently topological insulators (2004)

- not mentioned

Anderson localization
Kosterlitz-Thouless

## further insights

- Philippe Nozieres has a quote with which I heartily agree: ‘‘only simple qualitative arguments can reveal the underlying physics

- ....but the ones where we literally do not know what questions to ask! 

> You may not in the end solve them, but in the long run they are the
> ones really worth doing.

-  [in particular the fractional version - FQHE](https://knowen.org/nodes/28109)

> gave it an enormous fillip and at the same time introduced the **novel idea of quasiparticles, which bear no simple relation** either to the underlying particles (as do Landau quasiparticles in a Fermi liquid) or to the underlying classical waves (as do the phonons in a typical insulator).

- The impact of quantum information: as mentioned above, **I believe this will in the long run be profound**

> The present author would query whether the majority of the community has yet fully
> caught up with the implications of this mini-revolution

-  condensed matter physics to test the quantum mechanics of a macroscopic variable-(perhaps an **‘‘invisible” paradigm shift**..

> And as to the latter, it is topology, in
> the sense of the need for the wave function to be single-valued,
> which is at the root of just about every quantum phenomenon in
> many-body physics

## [Quantum Computation and Quantum Information](http://mmrc.amss.cas.cn/tlb/201702/W020170224608149940643.pdf)  Michael A. Nielsen & Isaac L. Chuang

## the problems

![xx](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5623/leggett-fig.png 'xx')

## 2022
⏎
[DAVID JAMES THOULESS ---- 21 September 1934 — 6 April 2019](https://royalsocietypublishing.org/doi/pdf/10.1098/rsbm.2021.0049)
⏎
# Parents

* Anthony J. Leggett

# Attachments

* [](https://knowen-production.s3.amazonaws.com/uploads/attachment/file/5623/leggett-fig.png)